[OpenSIPS-Users] Mediaproxy ICE negotiations

[John Quick]

Using Blink and other ICE compatible clients with Mediaproxy 2.x and
OpenSIPS 1.7.x, I have been looking at some packet captures and reading RFC
5245. I would like to get a deeper understanding of how ICE works and the
roles OpenSIPS and Mediaproxy play.

With Mediaproxy as a low priority "ice_candidate" (set using modparam) I can
see that OpenSIPS adds the address of the Mediaproxy to the list of ICE
candidates in the SDP. It sets the type to 'relay'. Devices that support ICE
are required to sort and select potential candidates then test connectivity
- one of the connectivity tests uses STUN requests. In my packet captures, I
could see the UAC sending STUN requests to candidates of type "host", but
did not see any sent to the Mediaproxy (this might have been because the
other candidates were higher priority). I wondered how Mediaproxy is able to
handle the STUN requests used during connectivity tests. Does it respond to
them directly or is it somehow able to relay the requests in the same way as
it would relay the RTP? Or should it never receive them because it is a
relay?

Is there any documentation I may have missed that explains this?

Thanks.

John Quick
Smartvox Limited
Web: www.smartvox.co.uk